Field of the Invention
The present invention relates to a method and apparatus for processing data which varies with time, for instance, pulse rates, and more particularly to a method and apparatus for stabilizing measured values for the purpose of display.
During recent years, an increasing number of people have been engaging in regular exercise in order to keep fit. It is said that exercise appropriate for the purpose of keeping fit is hard enough to keep pulse rates ranging from 70 to 80 percent of maximum pulse rates. In an attempt to meet a desire for measuring pulse rates during exercise, wrist watches equipped with pulse rate monitors have been produced and been commercially available. There are two different kinds of pulse rate monitors: that is, one using a photoelectric type detector and the other using an electrocardiograph type detector. In the former type detector pulse rates are determined electro-optically in terms of blood flow rates in a finger with the finger put on a photoelectric sensor, which is fixed to the casing of a wrist-watch. In the latter type detector pulse rates are determined in terms of electric potential appearing on a finger with the finger put on a cardiograph sensor, which is fixed to the casing of a wrist-watch, too. Also, there are two different methods of determining pulse rates on the basis of the signals supplied by the cardiograph sensor. One method might be called "direct measuring method", in which the number of pulse detection signals per minute is counted and the count is displayed as an instantaneous pulse rate (see Japanese Patent Application Laid-Open No. 59-91389). The other method might be called "interpulse period equivalent measuring method", in which the interpulse periods of two to ten pulse detection signals are measured, and then a pulse rate per minute is estimated on the basis of the interpulse periods thus determined.
In these conventional pulse rate measuring methods, however, there are problems which make conventional pulse rate meters difficult to handle.
Specifically, the "direct measuring method" takes as long as one minute to complete a single measurement. In this connection, the value of the pulse rate when displayed, is stable, but it takes too much time to permit the continuous measurement of pulse rate. In contrast, the "interpulse period equivalent measuring method" is essentially a sampling measurement conducted at regular intervals of two to ten pulses. Therefore, it requires as short a measurement time as would permit the continuous measurement of pulse rate. However, as usually observed in the sampling measurement, disadvntageously the sampled and measured value varies at each and every measurement, and therefore the result of measurement is hardly reliable because of their inconsistency.